The New Puberty:
Why are Girls Starting Puberty Earlier?

Most psychologists are aware that girls are entering puberty earlier than they did just a generation ago. In fact, teachers and health professionals spotted this trend in their classrooms and offices long before the research caught up. Now, science confirms that while age at menarche, or first period, is not much earlier than it was several decades ago, girls’ onset of breast and pubic hair development is starting at markedly younger ages.

In our ongoing longitudinal study, we followed 1200+ girls for almost 10 years and found that at age 7 years, a whopping 23% of African American girls, 15% of Latina girls, and 10% of non-Hispanic white girls already showed signs of early breast development. This is astonishing given that not long ago, pediatricians were deeply concerned when girls were developing breasts before age 8y. Many have described this as the “new normal” – a term that never sat well with us given the numerous deleterious outcomes associated with early puberty.

Early puberty has been linked to a host of short- and long-term negative health and emotional consequences. In adolescence, on average, early-maturing girls initiate sex, experiment with drug and alcohol use, are more likely to be depressed or anxious, and are more prone to have an eating disorder or display conduct problems compared to their later-developing peers. They also tend to have lower academic achievement. In adulthood, early puberty is associated with increased risk for breast cancer, obesity, cardiovascular disease and all-cause mortality (the term that means “dying from anything”).

Given the risks associated with early maturation, the two of us (an adolescent psychologist and a pediatric endocrinologist) struggled mightily with accepting that this trend toward earlier development should be considered a “new normal.” We felt that this diminished concern about the implications of entering puberty at tender ages, and detracted from the imperative to determine potential causes. So, our journey together started.

We moved upstream, along with a large multi-disciplinary team of colleagues, to investigate potential early determinants that might help explain this seemingly rapid shift in girls’ pubertal onset – one that was occurring much faster than the slow wheels of evolution could explain. We joined with epidemiologists, environmental health scientists, nutritionists, built environment experts and pediatricians to determine the root causes, and our results have been surprising.

The current research illuminates three main contributors to girls’ early puberty and perhaps to the secular trend towards puberty starting early. We introduce these here and will further unpack them in future posts. The primary culprit is girls’ body weight. As the US and other developed (and developing) countries have gotten heavier, girls’ puberty simultaneously has been starting earlier. Longitudinal research shows that higher prepubertal body mass predicts breast development and menarche at younger ages. The second suspect is environmental exposures, particularly endocrine disrupting chemicals (EDCs) that mimic estrogen in the body. This research is in its infancy, but there is compelling evidence from animal studies that we should be studying the effects of these EDCs more intensively in humans. They are ubiquitous in our environment and in our girls’ bodies as well, yet we know little about their direct effects, much less how they act in combination. Finally, exposure to stress, particularly within the family, has been linked to earlier development. Girls raised in homes characterized by unpredictable, inconsistent, or harsh circumstances are more likely to mature early.

Despite these grim findings, there are positive factors that have been shown to effectively offset or prevent at least some of these risks. One, which will not surprise clinicians, is changing the home environment to support a healthier childhood, from biological, developmental and psychological standpoints. We’ll dive down into some tips and tools that can help parents — and the practitioners who work with them — understand how to adjust their lives to prevent or slow down their daughters’ early puberty. And for girls who are already in the throes of puberty at young ages, there are also effective ways to help guide parents through this challenging but exciting time. There’s a lot to share, and we welcome you to The New Puberty!